Even though the industrial machines or sinks for the cleaning of mechanical parts have been used since the beginning of the industrial revolution, when the petroleum-based lubricants were invented, these are currently still in use, despite the environmental pollution problem they generate.
Typical industrial sinks for the cleaning of mechanical parts consist essentially of a bottom reservoir (usually a single 120 L metallic drum) from which a cleaning fluid is recycled to a washing sink using a submersible pump. In the washing sink, the user washes the part with the fluid, returning said already used cleaning fluid to the bottom reservoir through gravity.
The cleaning fluid is a hydrocarbon degreaser or naphtha, which, although initially is very effective in the waste removal due to its solvent capability, it is of little use regarding durability, since with only just 2% grease content it starts leaving greasy residues on the “washed parts”. Likewise, said cleaning fluid is made 100% by volatile organic compounds (VOCS), so it is highly air-polluting; in addition, it is flammable, and it is cataloged by the National Fire Protection Association (NFPA) within the risk 3 category in flammability and 2 in health. The above makes it necessary for this type of cleaners to be renewed frequently, and that the waste materials are disposed of according to the regulations for hazardous waste.
Similarly, these industrial sinks have other drawbacks such as the lack of instrumentation allowing the control or monitoring of the physicochemical variables such as temperature, pH, fluid level or aeration.
Based on the above, various systems and apparatus have been developed for the washing of mechanical or industrial parts, which include the use of microorganisms to achieve the cleaning of said pieces without having the above-mentioned drawbacks.
For example, the U.S. Pat. No. 6,057,147 describes a device consisting of a reservoir to clean hydrocarbon-polluted objects, which has means to enter a recyclable cleaning solution, which is recycled to wash the objects; means to drain the solution from the reservoir to a biochamber; and means to monitor said solution when it enters the biochamber. In turn, the biochamber contains means to aerate and stir the solution, as well as outlet means to a plurality of filters to filter the cleaning solution and remove sediments. The cleaning solution disclosed herein comprises aerobic microorganisms which degrade hydrocarbons, such as Achromobacter, Bacillus, Flavobacterium and Pseudomonas spp, among others.
Further, in U.S. Pat. No. 6,762,047 an aqueous composition is disclosed, which may be used in various apparatus or industrial sinks to remove oils, grease, etc., from mechanical objects, said composition comprises at least one species of Pseudomonas, as well as water, a non-ionic ethoxylated surfactant, an alkaline metal nitrate, and optionally, mono ammonia phosphate as buffer.
Similarly, U.S. Pat. No. 6,571,810 describes an apparatus for the washing of mechanical parts, which comprises a sink wherein the parts are contacted with a fluid; the sink is in communication with a tank having live microorganisms which degrade organic matter, such that the fluid is recycled in a closed environment. The apparatus also has a filter containing microorganisms fixed thereto, which is positioned in the tank. The microorganisms used can biodegrade organic compounds such as hydrocarbons, oils, grease, etc., and may be selected from those of the genera Bacillus, Micrococcus, Flavobacterium, among others. The filter works as a vehicle to contact microorganisms with the cleaning fluid, and it has microorganisms bonded together by a water-soluble encapsulating agent, which releases the microorganisms when the cleaning fluid is introduced into the filter. Referring to the cleaning fluid, it is compatible with the microorganisms such that they are able to live in the fluid (for example, a mixture of surfactants and emulsifiers having non-volatile organic compounds, phosphates, formaldehyde, biocides, etc.). Further, the apparatus comprises a submersible pump to recycle the cleaning fluid, a level signaling, a heater, a control panel, etc. The apparatus works as follows: the pump pumps the cleaner fluid from the tank to the sink, where the cleaning of the parts is carried out.
While the systems for the washing of parts described above (including the use of biodegradable cleaners having various microorganisms) allow to reduce the environmental issues associated with the use of solvents and waste-disposal, they continue having certain disadvantages.
These disadvantages include the need to replace the degreaser or cleaner frequently (every three to four days), since this becomes saturated with pollutants and starts an anaerobic decomposition process, releasing bad odors. In addition, the cleaning fluid used must be disposed of as hazardous waste, since despite of being biodegradable, being saturated with used lubricant, the whole liquid is considered as hazardous waste.
In addition, the industrial apparatus or sinks for the cleaning of mechanical parts working under the same liquid recycling principle, and which use the bioremediation process for grease and oils, are usually manufactured from high density polyethylene plastic (HDPE), thus being more prone to suffer damages while in use, since the metallic nature of the mechanical parts in the end causes the breaking of the sink surface.
Another disadvantage is that the existing industrial sinks operate under physicochemical conditions focused on trying to optimize bioremediation with microorganisms, thereby generating a higher energy consumption (as the working temperature commonly used is about 41° C.) resulting uncomfortable to the operators; in addition, this also causes the short-term evaporation of the perfume used to make the use of the cleaning fluid more pleasant (less than a week), generating bad odors within a month, or even earlier.